If Iran wanted Chinese help the time to do it was years ago
The Chinese have no reason to jump in as a savior for Iran at this stage, there is no ethnic or cultural or strategic aim that would justify right now
Ever since world war 2 I don't know why people don't understand this. Look at all the wars since 9/11 I am sure each stage people said why don't the Russians jump in
Then recently with Syria everyone said why did the Russians leave?
The point is you can only do so much without compromising your own integrity and strength
Let us also say this, with nation states even when you help someone you are mindful to the extent that one day they can become more powerful and influential than you might be comfortable with
That is not anti Iranian that is just the calculus of real politik, and selfish nation state's.